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The Diagnostic Interval of Colorectal Cancer Patients in Ontario by Degree of Rurality

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The Diagnostic Interval of Colorectal Cancer Patients in Ontario by Degree of Rurality THE DIAGNOSTIC INTERVAL OF COLORECTAL CANCER PATIENTS IN ONTARIO BY DEGREE OF RURALITY by Leah Hamilton A thesis submitted to the Graduate Program in the Department of Public Health Sciences in conformity with the requirements for the Degree of Master of Science Queen’s University Kingston, Ontario, Canada (September, 2015) Copyright ©Leah Hamilton, 2015 Abstract Background: Wait times while moving through the cancer diagnostic process are a public health concern. Rural populations may experience more challenges in accessing cancer care, which could translate into a longer diagnostic interval and represent a healthcare inequity. This project analyzed the association between rurality of residence and the diagnostic interval of colorectal cancer (CRC) patients in Ontario, Canada. Methods: This was a retrospective population-based cohort study. We used administrative databases available through the Institute for Clinical Evaluative Sciences (ICES) to identify incident CRC cases diagnosed from Jan 1, 2007- May 31, 2012. We assigned each patient a rurality score, based on their census subdivision, and calculated the length of their diagnostic interval. We defined the diagnostic interval as the time (in days) between a patient’s first diagnostic-related encounter with the health care system to the CRC diagnosis date. Data linkage through ICES allowed us to describe variations in cancer stage and the diagnostic interval by degree of rurality of patient residence and to analyze associations through multivariable models taking into account potential confounders. Results: Overall, the median diagnostic interval of the CRC cohort was 64 (IQR: 22-159) days and the 90th percentile was 288 days. Patients with stage I CRC had a longer median diagnostic interval than patients with stage IV CRC. Across rurality categories, a significant difference in median diagnostic interval was detected in the stage I stratum only, ranging from 58.5 to 108 days (p=0.0005), but with the most rural group having the shortest diagnostic interval. Results from adjusted multivariable models suggested that patients in mid-ranged rural categories had similar or longer diagnostic intervals compared to patients in the least rural category while patients in the most rural category maintained the shortest diagnostic intervals. Important covariates included age, comorbidities and CRC sub-site. Conclusion: Our results do not support a rurality effect on stage or the diagnostic interval in the hypothesized direction. Estimates of a shorter interval in the most rural category, especially for stage I ii disease, call for a deeper analysis to better understand care delivery in those areas and patient characteristics that might affect the interval. iii Co-Authorship This thesis is the work of Leah Hamilton in collaboration with her supervisor Dr. Patti A. Groome and collaborator Ms. Colleen E. Webber. Thesis design represents the work of Leah Hamilton, Dr. Patti A. Groome and Ms. Colleen E. Webber. The clinical consultant, Dr. Geoffrey A. Porter, provided advice and clinical insights throughout the thesis. Dr. Jennifer A. Flemming was consulted while creating the CRC symptom status algorithm and Dr. Hugh Langley provided insight on fecal occult blood test (FOBT) Ontario Health Insurance Plan (OHIP) fee codes. Ms. Marlo Whitehead, senior analyst at the Institute for Clinical Evaluative Sciences (ICES) Health Services Research Facility at Queen’s University, performed the database linkages and data cuts. Thesis writing, statistical analyses and interpretations were the work of Leah Hamilton with guidance and suggestions from Patti A. Groome and Colleen E. Webber. Editorial feedback was also provided by Patti A. Groome, Colleen E. Webber and Dr. Geoffrey A. Porter. iv Acknowledgements It has been a true pleasure to work and learn from so many individuals throughout the duration of this thesis project. The efforts of numerous people went into this final piece of work and I am sincerely grateful. Firstly, I would like to thank my supervisor, Dr. Patti Groome, for making this project possible. Her consistent guidance and support as well as her epidemiological expertise and dedication to student mentorship allowed me to conceptualize and complete this thesis. Dr. Groome has a gift for teaching / “academic translating” that I have benefitted from greatly. I will take much learning from both the thesis and weekly lab meetings with me in the future. I would also like to thank Ms. Colleen Webber, my thesis collaborator-extraordinaire. Ms. Webber was a part of every meeting, e-mail and draft of the thesis project and the end product truly benefitted from her input and perspective starting from day one. I will always appreciate being able to wheel my chair over to her desk to recap on the latest decisions and feedback. This project also greatly benefited from the clinical expertise and insight of Dr. Geoffrey Porter, the clinical consultant for the thesis. Dr. Porter provided invaluable feedback throughout the thesis process. I would also like to thank Dr. Jennifer Flemming and Dr. Hugh Langley for their clinical feedback. This project would not have been possible without the help of the Institute for Clinical Evaluative Sciences (ICES) staff; in particular Ms. Marlo Whitehead and Ms. Susan Rohland. I thank Ms. Whitehead for her patience through the many iterations of the project’s dataset creation plan and for my daily interruptions during the analysis phase with requests for data transfers and coding questions. I thank Ms. Rohland for her encyclopedic knowledge of all things ICES-privacy and ethics-related as well as her dedication to following-up on ongoing processes/approvals. A big thank you to the Groome Lab (Ally Mahar, Colleen Webber, Li Jiang, Kim Foley, John Queenan and Graham Smith) at Cancer Care and Epidemiology (CCE) for creating such a great work environment. I truly valued the support, enthusiasm and feedback for my project both during lab meetings v and in our pod. Thank you to my classmates in the Department of Public Health Sciences, who made my time in Kingston so enjoyable and who I relied on during all phases of the program. I would also like to acknowledge the financial support from the Department of Public Health Sciences/Queen’s Graduate Program and from Dr. Patti Groome. Finally, I need to thank my parents, sisters, housemates and friends for their endless support, love and encouragement. vi Table of Contents Abstract ......................................................................................................................................................... ii Co-Authorship.............................................................................................................................................. iv Acknowledgements ....................................................................................................................................... v List of Figures .............................................................................................................................................. xi List of Tables .............................................................................................................................................. xii List of Abbreviations ................................................................................................................................. xiv Chapter 1 Introduction .................................................................................................................................. 1 1.1 Background and Rationale .................................................................................................................. 1 1.2 Study Design Overview ...................................................................................................................... 2 1.3 Study Objectives ................................................................................................................................. 2 1.4 Thesis Outline ..................................................................................................................................... 3 Chapter 2 Literature Review ......................................................................................................................... 4 2.1 Colorectal Cancer ................................................................................................................................ 4 2.1.1 Epidemiology ............................................................................................................................... 4 2.1.2 Biology ......................................................................................................................................... 5 2.1.3 Risk Factors ................................................................................................................................. 7 2.1.4 Signs and Symptoms .................................................................................................................... 9 2.1.5 Diagnostic Investigations and the Diagnostic Pathway ............................................................. 10 2.1.6 CRC Stage .................................................................................................................................. 12 2.2 CRC Diagnostic Interval ................................................................................................................... 14 2.2.1 Definition ..................................................................................................................................
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